1. Field of the Invention
The invention relates to the fabrication of structures with nanometer scale dimensions.
2. Description of the Prior Art
Lithography is generally used in conjunction with wet or dry etching procedures to define trenches for isolation, fluid flow, and narrow electrode devices in semiconductors and insulators. The ultimate widths of the resulting structures is determined by the minimum feature size of the lithography process, and, for photolithography, is limited by the diffraction of light. What is needed is an alternative method of fabricating sub-wavelength features in semiconductors and insulators.
The invention is a method for forming a nano-scale trench in a substrate comprising the steps of disposing a first masking layer having a thickness, d, on a surface of the substrate. The first masking layer is then patterned according to design choice. Any pattern may be employed. Whereas the illustrated embodiment shows a multiple number of straight lines used to define trenches or channels, any curvilinear pattern forming a connected or disconnected network may be chosen consistent with the technique of shadow or directional evaporative deposition. A second masking layer is disposed on the patterned first masking layer using angled deposition of the second masking layer to define an exposed trench window through the second masking layer by shadow deposition relative to the first masking layer. The trench is defined into the substrate through the exposed trench window. The first and second masking layers are removed to leave a trenched surface of the substrate, which may then be used in subsequence processing steps to make channels, wires and other nano-scale structures.
A repeated cycle of the forgoing steps after the processed substrate has been rotated, can define trenches in the substrate at a different angle depending on the rotation. For example, straight trenches crossing each other at right angles can be formed by repeating the process steps twice in two cyclic groups to produce a grid of trenches if desired.
The step of defining the trench into the substrate through the exposed trench window comprises directionally etching the trench into the substrate in a direction substantially perpendicular to the plane of the substrate.
The step of defining the trench into the substrate through the exposed trench window defines a trench window of width w, where w=d sin xcex8 and where xcex8 is the angle of incidence of the angled deposition of the second masking layer.
The step of disposing the second masking layer on the patterned first masking layer using angled deposition of the second masking layer comprises disposing the second masking layer by directional evaporation of material composing the second masking layer.
The method further comprises disposing a sealing layer over the trench to hermetically seal the trench to define a fluidic channel, which sealing layer in one embodiment is an elastomeric layer.
The method further comprises the step of disposing a cantilever over the trench. The cantilever completely crosses the trench but may or may not be in contact with both sides of the substrate surface on opposite sides of the trench, in other words, the possibility exists that the cantilever may extend over, but not be in actual contact with one side of the surface of the substrate on opposite sides of the trench. In one embodiment the cantilever is a polymeric molecule disposed over the trench, such as a DNA molecule. In another embodiment the cantilever may be a carbon nanotube. The method further comprises the step of disposing a conductive layer onto the cantilever to form a bridge to electrically connect adjacent contact regions separated by the trench. In the illustrated embodiment the method comprises the step of forming the adjacent contact regions separated by the trench simultaneously with the bridge.
The method further comprises the step of disposing a conductive layer into the trench to form a wire. In one embodiment the step of disposing the conductive layer into the trench to form the wire comprises disposing the conductive layer onto the planar surface of the substrate and into the trench and then removing the conductive layer from the planar surface of the substrate.
The invention is also characterized as the structure or apparatus formed by the above methodology.
While the method has been described for the sake of grammatical fluidity as steps, it is to be expressly understood that the claims are not to be construed as limited in any way by the construction of xe2x80x9cmeansxe2x80x9d or xe2x80x9cstepsxe2x80x9d limitations under 35 USC 112, but to be accorded the full scope of the meaning and equivalents of the definition provided by the claims. The invention can be better visualized by turning now to the following drawings wherein like elements are referenced by like numerals.